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3. Topotactic phase transformation of lithiated spinel to layered LiMn0.5Ni0.5O2: the interaction of 3-D and 2-D Li-ion diffusion.

Author

Shi, Boyu, Gim, Jihyeon, Li, Tianyi, Koirala, Krishna, Wang, Chongmin, Hou, Dewen, Liu, Yuzi, Jorne, Jacob, Croy, Jason R., Thackeray, Michael M., and Lee, Eungje

Abstract

This study investigates the structural evolution of LiMn0.5Ni0.5O2 cathode materials for Li-ion batteries as a function of synthesis temperature and its effect on electrochemical performance. It is demonstrated that, as the synthesis temperature increases from 400 to 900 °C, a gradual topotactic transformation occurs between a lithiated spinel structure, denoted herein as "lithium-excess spinel" LxS-LiMn0.5Ni0.5O2 (or LxS-LMNO), and the well-known layered LiMn0.5Ni0.5O2 structure prepared at high temperature, HT-LiMn0.5Ni0.5O2 (HT-LMNO). The electrochemical capacity of the LiMn0.5Ni0.5O2 electrodes follows a parabolic trend with increasing synthesis temperature, which is attributed primarily to the gradual transformation of 3-dimensional (3-D) to 2-dimensional (2-D) diffusion pathways for the Li ions. When synthesized at 400 °C, LxS-LiMn0.5Ni0.5O2 electrodes perform well, benefitting from the 3-D network of channels within the LxS structure. By contrast, when prepared at 500–700 °C, LiMn0.5Ni0.5O2 electrodes operate poorly, which is attributed to the formation of locally disordered structural arrangements that impede Li-ion diffusion. Such an increase in local disorder in the mid-temperature synthesis range is attributed to the structural frustration between the lithium-excess spinal and layered end-members. The transformation from the locally disordered to more ordered layered components between 700 °C and 900 °C enhances electrochemical performance. The study opens new avenues for designing next-generation Mn-rich cathode materials by fine-tuning the synthesis conditions as well as the composition and structure of LxS-LMNO electrodes. [ABSTRACT FROM AUTHOR]

Published
2025
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4. High‐Energy LiNiO2 Li Metal Batteries Enabled by Hybrid Electrolyte Consisting of Ionic Liquid and Weakly Solvating Fluorinated Ether.

Author

Liu, Qian, Xu, Jiayi, Jiang, Wei, Gim, Jihyeon, Tornheim, Adam P., Pathak, Rajesh, Zhu, Qijia, Zuo, Peng, Yang, Zhenzhen, Pupek, Krzysztof Z., Lee, Eungje, Wang, Chongmin, Liu, Cong, Croy, Jason R., Xu, Kang, and Zhang, Zhengcheng

Subjects
ENERGY density, DENSITY functional theory, RESEARCH personnel, ELECTROLYTES, DYNAMIC simulation, ELECTRIC batteries, LITHIUM cells
Abstract

In pursuit of the highest possible energy density, researchers shift their focus to the ultimate anode material, lithium metal (Li0), and high‐capacity cathode materials with high nickel content (Ni > 80%). The combination of these aggressive electrodes presents unprecedented challenges to the electrolyte. Here, we report a hybrid electrolyte consisting of a highly fluorinated ionic liquid and a weakly solvating fluorinated ether, whose hybridization structure enables the reversible operation of a battery chemistry based on Li0 and LiNiO2 (Ni = 100%), delivering nearly theoretical capacity of the latter (up to 249 mAh g−1) for >300 cycles with retention of 78.6% and in absence of unwanted morphological changes in both electrodes. Extensive characterization assisted by molecular dynamic simulation and density functional theory calculations reveals the function of the fluorinated ether to be far more profound than simple dilution and viscosity reduction. Instead, it induces drastic changes in Li+‐solvation environment, the consequence of which engenders simultaneous stabilization of electrode/electrolyte and interfacing via formation of respective interfacial chemistries. This study further unlocks fundamental knowledge underneath the prevailing "diluent strategy" that is extensively applied by the electrolyte researchers and opens more design space for the next‐generation electrolytes and interphases for these coveted battery chemistries. [ABSTRACT FROM AUTHOR]

Published
2024
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6. Surface Structure, Morphology, and Stability of Li(Ni1/3Mn1/3Co1/3)O2 Cathode Material

Author

Garcia, Juan C, Bareño, Javier, Yan, Jianhua, Chen, Guoying, Hauser, Andrew, Croy, Jason R, and Iddir, Hakim

Subjects
Affordable and Clean Energy, Chemical Sciences, Engineering, Technology, Physical Chemistry
Abstract

Layered Li(Ni1-x-yMnxCoy)O2 (NMC) oxides are promising cathode materials capable of addressing some of the challenges associated with next-generation energy storage devices. In particular, improved energy densities, longer cycle-life, and improved safety characteristics with respect to current technologies are needed. However, sufficient knowledge on the atomic-scale processes governing these metrics in working cells is still lacking. Herein, density functional theory (DFT) is employed to predict the stability of several low-index surfaces of Li(Ni1/3Mn1/3Co1/3)O2 (NMC111) as a function of Li and O chemical potentials. Predicted particle shapes are compared with those of single crystal NMCs synthesized under different conditions. The most stable surfaces for stoichiometric NMC111 are predicted to be the nonpolar (104), the polar (012) and (001), and the reconstructed, polar (110) surfaces. Results indicate that intermediate spin Co3+ ions lower the (104) surface energy. Furthermore, it was found that removing oxygen from the (012) surface was easier than from the (104) surface, suggesting a facet dependence on surface-oxygen vacancy formation. These results give important insights into design criteria for the rational control of synthesis parameters as well as establish a foundation on which future mechanistic studies of NMC surface instabilities can be developed. (Figure Presented).

Published
2017

12. LT-LiNi1/3Mn1/3Co1/3O2: A Partially-Disordered, Composite Rock Salt Cathode Prepared by Flame Spray Pyrolysis for Li-Ion Batteries

Author

Ku, Kyojin, primary, Han, Jinhyup, additional, Li, Linze, additional, Gim, Jihyeon, additional, Park, Jehee, additional, Shi, Boyu, additional, Liang, Yujia, additional, Stark, Anthony, additional, Wang, Chongmin, additional, Croy, Jason R., additional, Thackeray, Michael, additional, Libera, Joseph, additional, and Lee, Eungje, additional

Published
2023
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15. Redox Mechanisms and Migration Tendencies in Earth-Abundant 0.7Li2MnO3·0.3LiFeO2Cathodes: Coupling Spin-Resolved X-ray Absorption Near Edge and X-ray Absorption Fine Structure Spectroscopies

Author

Kwok, Chun Yuen, Mallick, Subhadip, Pollock, Christopher J., Gutierrez, Arturo, Dixit, Marm, Croy, Jason R., and Balasubramanian, Mahalingam

Abstract

We report the use of iron 1s3p resonant X-ray emission processes to conduct spin-selective, high-energy resolution fluorescence detected X-ray absorption near-edge spectroscopy (HERFD-XANES) on an iron-containing, lithium- and manganese-rich, fully earth-abundant cathode material, Li1.3Mn0.5Fe0.2O2(0.7Li2MnO3·0.3LiFeO2). Coupling this technique with conventional Mn K-edge XANES and detailed extended X-ray absorption fine structure (EXAFS) analysis from both the Mn and Fe vantage points, we gain fundamental insights into the redox processes and migration tendencies of transition metals in this cathode material at the bulk level. We show that during the first charge, Fe3+undergoes oxidation to form Fe4+prior to the activation plateau. Toward the end of activation, a significant fraction of the iron is present as tetrahedral Fe3+. This observation reveals that iron migration from octahedral to tetrahedral sites and iron reduction are initiated during activation. Upon first discharge from the activated state, a continuous and overlapping reduction of both Fe and Mn is observed, with Fe largely restored back as an octahedrally coordinated Fe3+. The manganese local environment gradually changes to a distorted cooperative Jahn–Teller Mn3+structure during discharge, with the clear presence of two Mn–O as well as two Mn–Mn correlation distances at 2.0 V. The significant reduction of manganese in the very first discharge is distinctly different from that seen in typical nickel-based lithium-manganese-rich materials but is similar to that observed for pure Li2MnO3. These findings shed light on key structure–property correlations in the cathode material and point to a causative relationship between the redox mechanisms as well as structural changes endured by the material and relatively poor performance during extended electrochemical cycling.

Published
2024
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18. Performance Optimization of High Ni (≥90%) Cathode Materials: Synthesis & Modification

Author

Gim, Jihyeon, primary, Han, Jinhyup, additional, Kahvecioglu, Ozgenur, additional, Zuo, Peng, additional, Zou, Lianfeng, additional, Dogan, Fulya, additional, Mane, Anil U., additional, Darapaneni, Pragathi, additional, Wang, Chongmin, additional, Elam, Jeffrey W., additional, Lee, Eungje, additional, Amine, Khalil, additional, and Croy, Jason R., additional

Published
2022
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35. New synthesis strategies to improve Co-Free LiNi0.5Mn0.5O2 cathodes: Early transition metal d0 dopants and manganese pyrophosphate coating

Author

Darbar, Devendrasinh, primary, Self, Ethan C., additional, Li, Linze, additional, Wang, Chongmin, additional, Meyer, Harry M., additional, Lee, Changwook, additional, Croy, Jason R., additional, Balasubramanian, Mahalingam, additional, Muralidharan, Nitin, additional, Bhattacharya, Indranil, additional, Belharouak, Ilias, additional, and Nanda, Jagjit, additional

Published
2020
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42. LT-LiMn0.5Ni0.5O2: a unique co-free cathode for high energy Li-ion cells.

Author

Shi, Boyu, Gim, Jihyeon, Li, Linze, Wang, Chongmin, Vu, Anh, Croy, Jason R., Thackeray, Michael M., and Lee, Eungje

Subjects
CATHODES, OXIDATION-reduction reaction, LOW temperatures, HIGH voltages
Abstract

A novel LiMn0.5Ni0.5O2 cathode with a predominant, partially-disordered lithiated-spinel structure has been prepared by a 'low temperature' (LT) synthesis. Li/LT-LiMn0.5Ni0.5O2 cells operate between 5.0 and 2.5 V with good cycling stability, yielding a capacity of 225 mA h g−1, principally by redox reactions on the nickel ions on distinct voltage plateaus at ∼3.6 V and ∼4.6 V. [ABSTRACT FROM AUTHOR]

Published
2021
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43. Critical Barriers to Successful Implementation of Earth-Abundant, Mn-Rich Cathodes for Vehicle Applications and Beyond: A Detailed Study of Low SOC Impedance.

Author

Jiajun Chen, Gutierrez, Arturo, Saray, Mahmoud Tamadoni, Yassar, Reza Shahbazian, Balasubramanian, Mahalingam, Yan Wang, and Croy, Jason R.

Subjects
SUSTAINABLE chemistry, SURFACE preparation, SURFACE impedance, ELECTRODES, ELECTROLYTES
Abstract

Earth-abundant, sustainable cathode chemistries based on Mn are increasingly attractive for enabling a broader portfolio of cathode oxides. The well-known class of lithium- and manganese-rich cathodes still represents very viable options. However, despite the important work on understanding the mechanisms of voltage fade, hysteresis, and oxygen activity, relatively little attention has been given to understanding the impedance characteristics of these electrodes. In particular, an anomalous rise in area specific impedance at lower states of charge, as well as overall impedance rise and surface damage due to electrolyte interactions, represent critical barriers to implementation. This work presents a comprehensive study of impedance behavior in cobalt-free, lithium- and manganese-rich electrodes. The use of a robust surface treatment allows for long-term behavior to be probed in the absence of surface damage, capacity loss, and impedance rise due to electrolyte interactions. The anomalous rise in impedance could not be correlated to surface changes, or surface phase formation, but could be directly correlated with the bulk processes of voltage fade and voltage hysteresis. The activated material can be explained as a percolating network of higher-voltage, layered-type sites having facile Li diffusion. Interspersed throughout this network are lower-voltage, disordered sites that represent a significant barrier. [ABSTRACT FROM AUTHOR]

Published
2021
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